Electrochemical gas sensor systems are used for stationary or mobile monitoring tasks in industry, especially for monitoring harmful gas concentrations in chemical or petrochemical plants. In usual technical implementations, electrochemical gas sensor systems are composed of an electrochemical gas sensor with a sensor housing and a corresponding electronic operating and analyzing unit. Via a gas inlet, for example, a gas-permeable membrane, gas enters the sensor housing from a measuring environment. An electrochemical gas sensor with a measuring electrode, an auxiliary electrode, a reference electrode and a protective electrode for measuring oxygen is known from DE 198 45 318 C2. A measuring electrode, an auxiliary electrode, a reference electrode and a protective electrode are arranged in an electrolyte space filled with sulfuric acid as a liquid electrolyte. Both the measuring electrode and the protective electrode are also often called working electrode. The electrodes are electrically connected with an electronic operating unit, a so-called potentiostat. An equivalent electric potential is set on the measuring electrode and the protective electrode against a reference potential on the reference electrode by means of the potentiostat during the operation of the electrochemical gas sensor.
An electrochemical gas sensor with a measuring electrode made of carbon nanotubes and with an auxiliary electrode in an aqueous lithium bromide electrolyte for detecting hydrocyanic acid is known from DE 10 2010 021 975 A1. In an electrochemical gas sensor according to DE 10 2010 021 975 A1, the electric potential is set at the measuring electrode such that lithium bromide reacts to form bromine and dissolved bromine is thus present in the electrolyte. With this method for generating dissolved bromine, there is a basic current in the electrochemical gas sensor, which current depends on the electric potential set and has therefore an adverse effect on the sensitivity and the basic current stability of the electrochemical gas sensor.